To reduce the cost of the solenoid drive electronics, saturated type drivers are preferred over peak and hold current drivers. However, saturated type drivers significantly increase the power consumed due to their sustained current level. This power consumption results in greater heat generation. A minimum coil resistance (which is much higher than that allowable with a peak and hold driver) is necessary to limit the heat rise. Though a high resistance pulse width modulator (PWM) contains more turns for a given package space, the current rises much more slowly and truncates at a lower level than for a low resistance PMW, resulting in less magnetic force for the same period of time and thereby increasing the time needed to close the armature against the coacting pole piece. This increased time reduces the overall performance of the armature and makes the internal design of the pulse width solenoid more critical. It was the search for an adequate pulse width modulated solenoid design for a saturated type driver which gave rise to the inventive design disclosed herein.
Accordingly, the invention as herein disclosed is primarily directed to the solution of the aforestated as well as other related and attendant problems of the prior art.